1. Field of the Invention
This invention relates to systems enabling the remote detection and identification of objects.
2. Description of the Prior Art
Numerous systems utilizing some form of electromagnetically responsive tag or marker affixable to an object to be detected and/or identified are known in the art. For example, passive tags, i.e., those not having an internal source of power and which are thus incapable of directly producing an electromagnetic field, are capable of responding to an external electromagnetic field in a manner enabling remote electrical detection. Typically, one such general type of passive electrical circuit comprises some form of a tuned inductive-capacitive circuit such that when stimulated by an external electromagnetic field the resonant frequency of the tuned circuit can be detected. Various schemes for so stimulating and detecting LC resonant tags are, for example, set forth in U.S. Pat. Nos 2,693,525 (Kendall), 2,910,579 (Jones & Currie), 3,299,424 (Vinding), 3,406,391 (LeVon), 3,624,631 (Chomet), 3,713,102 (Martin) and 3,740,742 (Thompson).
In such prior art identification and/or detection systems, the manner of attachment of the tag to the object to be identified and/or detected has been somewhat incidental. All such systems have, however, required that the object be directly handled in order to affix the tag to the object such as by mechanical fasteners, adhesives, insertion of the tag into the object and the like.